The focus of this proposal is to study the rhodopsin/transducin interface. Synthetic peptides and peptide analogs derived from transducin and rhodopsin will be used as specific ligands for high resolution structural studies (TRNOE and CPMAS NMR) when complexed to their respective partners. By defining the interacting surfaces during photoactivation, an increased understanding of the molecular mechanisms of rhodopsin/transducin complexation is sought. The information derived on the three-dimensional structure of the rhodopsin/transducin complex can assist in devising approaches for treating human diseases (retinitis pigmentosa and night blindness) associated with mutations in rhodopsin.